Radio frequency (RF) signals are commonly used for transmitting and receiving communications wirelessly. Antenna design has played an integral part in technological advancements made with respect to radio communications. Conventionally, a single antenna element such as a dipole antenna has provided an omnidirectional gain, at least within a particular dimensional plane (e.g., the earth's surface). Omnidirectional gain may be characterized by an antenna transmitting somewhat equal amounts of electromagnetic radiation in all directions within the plane, or likewise being equally sensitive to receiving radio frequencies from sources at equal distances around the antenna.
Clusters of antenna elements transmitting related signals, called array antennas, have been known to strengthen and/or weaken the collective gain of RF signals in particular directions and/or at particular times. For example, four antenna elements transmitting the same signal placed at strategic locations near each other (e.g., one half wavelength apart), may produce a beam, or strengthened gain, within a particular direction extending out from the antenna. Likewise, other directions achieve diminished gain. This is due at least in part to constructive and destructive interference caused by electromagnetic waves emitted from or transmitted to nearby elements. The effect can extend the reach of an array antenna over greater distances or into and through obstacles such as buildings. The effect can also be used to position areas of diminished gain so as to avoid disruptive radio sources or reflections in particular directions.
Advanced array antennas controlled by digital signal processors can adaptively modify the direction and strength of beams by, for example, making slight modifications to the phase of signals transmitted or received by the various elements of an array antenna. This process is referred to as beamforming, and beams formed in this fashion can extend the range of the array antenna beyond the normal omnidirectional range under equal transmitted power that the antenna might otherwise be limited to. Beamforming techniques have been used to extend the reach of an antenna and also to reduce the interference to the environment in order to maintain ongoing communications with a remote wireless subscriber. However, acquiring connections to wireless subscribers has been limited to the smaller omnidirectional range of the array antenna. This prevents the array antenna from acquiring connections to subscribers outside the omnidirectional range, but within the reach of beams.